Image processing technology has advanced significantly in recent years. One important area of advancement is in the processing of holographic images. The process of storing data in a holographic image or hologram involves storing a Fourier transform of a two-dimensional image of the data in an object plane on a recording medium such as a film or other device. To retrieve the stored data, the image is reconstructed by an inverse Fourier transform and captured with an electronic imager. The accuracy of the data storage and retrieval depends to a significant degree on the accuracy, from pixel to pixel, of the reconstructed image. In this process, image distortion often occurs. This distortion is primarily of a geometric form. For example, the image may be shifted or magnified or in some other way geometrically disturbed. In some other cases, the image may assume a curved distortion known as pin cushion or barrel distortion.
In an image affected by pin cushion distortion, the boundaries of a square image may be curved inwardly to the image center. For barrel distortion, the boundaries curve outwardly. The pin cushion and barrel distortions that appear in the image associate with imperfections that may exist in one or more of the lenses that reconstructs the image. These and other forms of distortion are difficult to compensate for on a pixel-by-pixel basis in the holographic image.
Other problems that arise in reconstructing holographic images include effects from misregistration, misalignment, improper magnification, image tilting, and other forms of geometric distortion. These different types of distortion prevent employing a simple recovery algorithm in which every pixel in the image corresponds to the same pixel in the object. No known method or system for accurately reconstructing the object image has acceptable image reconstruction speed or low data processing overhead to make holographic data storage a viable technology.